1. Field of the Invention
This invention concerns apparatus for distributing the weight bearing on the lower back of an individual in the seated position. The invention is particularly helpful for individuals with chronic lower back pain. While the invention is described in the context of a chair, it may also be implemented in other seating platforms including benches and automobile, train and airplane seats where people with chronic back pain must remain seated for prolonged periods.
2. Background Information
The lumbar spinal vertebrae are individual bones in the lower back which are separated from one another by intravertebral discs which function as shock absorbers. The flexibility of the vertebrae comprising the spinal column is controlled to a large extent by the discs, while the stability of the column is maintained in large measure by muscles and ligaments appropriately positioned along the spinal column. Each vertebra consists of a body with which the adjacent discs are in direct contact and posterior portions offset behind the main body, sometimes referred to as facet joints. Basically, the discs cushion the vertical pressure on the spinal column, while the facet joints prevent slippage of one vertebrae on another. They do, however, absorb some vertical pressure.
In childhood and early adult life, each disc consists of a fairly tough outer casing and a soft core or central portion. As the years pass, and depending upon the degree of physical stress imposed on the spine, a process of gradual deterioration occurs in the discs. Partial dehydration of the soft core causes partial shrinkage of the discs, and in the process, loss of some of their shock-absorbing capability. This results in a settling effect of one vertebrae on the next and in an increasing weight bearing on the facet joints of the vertebrae. This increasing pressure on the contact surfaces of those joints as a result of the loss of the shock-absorbing capability of the discs leads to reactive wearing down of the cartilagenous plates on the facet joints"" contact surfaces with resulting exposure of the outer surfaces of the bones that are normally protected by the cartilagenous plates. This exposure causes irregular outgrowth of the bone referred to as reactive spurring and sclerosis, resulting in a roughening of the contact surfaces. Such compromised surfaces are more vulnerable to injury or trauma than are the young healthy joints, and when these worn surfaces on the vertebrae are so injured, that often results in considerable lower back pain, requiring protracted periods of treatment. In essence, the facet joints of the vertebrae so injured can cause long periods of fluctuating discomfort which increases with greater levels of activity and, particularly, with repeated or sustained bending or lifting movements. Obesity, pregnancy and other situations which tend to increase the lumbar lordosis can further aggravate the problem of excessive facet joint pressure.
It is known that controlling the lordotic or forward convex curve in the lumbar area of the spine can favorably effect the pressure on the facet joints of the vertebrae, and that such control can rather easily and effectively be achieved through forced contraction of the psoasis major muscles that occupy each side of the lumber spine.
Only relatively recently has it been recognized that forced contraction of the psoasis major muscles may be accomplished by fixing or restraining the fronts or anterior portions of the thighs proximate the knees against upward movement when an individual is in the seated position and presses down with his/her feet. Apparatus for achieving such contraction in order to maintain optimum lumbar spinal alignment while seated is disclosed in my patent U.S. Pat. No. 4,768,834, the contents of which are hereby incorporated by reference herein.
Suffice it to say that in accordance with that patented arrangement, the legs of an individual sitting in a seat are strapped to the seat at locations proximate to the individual""s knees so as to maximize the effective lever arm of the thighs in contracting the psoas major muscles. When an individual is restrained in this manner, he or she may force his or her thighs upwardly against the strap while the balls of the feet are pressed downwardly against the surface supporting the seat so as to contract the upper lumber portions of the psoas major muscles. This forced contraction of those muscles causes them to function as lumbar flexors that flatten the lumbar spine. This helps the individual to achieve and maintain optimum lumbar spinal alignment while seated and is effective in relieving chronic back pain.
While that prior arrangement does operate satisfactorily, it does have certain drawbacks. More particularly, the restraining means is in the form of a retractable seat belt whose free end must be secured in order to restrain the seated individual""s thighs. This can pose a problem for elderly or infirm people, particularly those with arthritis in the joints of the hands and arms.
That prior apparatus is also relatively expensive to implement because it incorporates a retractor which requires a spring loaded ratcheting mechanism.
Accordingly, it would be desirable to be able to provide an improved and less expensive apparatus for maintaining optimal lumbar spinal alignment while seated.
It is an object of the present invention to provide an improved seat for maintaining optimum lumbar spinal alignment of a person sitting in the seat.
Another object of the invention is to provide a seat of this type which is easy to use even by old or infirm individuals.
A further object of the invention is to provide such a seat which is relatively easy and inexpensive to retrofit to otherwise more or less conventional seating platforms.
Other objects will, in part, be obvious and will, in part, appear hereinafter.
The invention accordingly comprises the features construction, combination of elements and arrangement of parts which will be exemplified in the following detailed description, and the scope of the invention will be indicated in the claims.
Briefly, the present apparatus comprises a seating platform which may be part of a more or less conventional chair, bench or the like, and is preferably height-adjustable. Rotatably mounted to the seating platform at opposite sides thereof is a pair of fore and aft extending axles. The forward ends of those axles extend just beyond the forward edge of the seat and are connected to a pair of mirror image thigh restrainers. Each such restrainer comprises a relatively wide J-shaped shell which is necked down to adjustably connect to the corresponding axle. The thigh restrainers are rotatable on their axles from a stowed position wherein they repose below the seat to an upright position wherein they engage over the thighs of an occupant of the seat. In the latter position, the occupant may force his/her thighs upward against the thigh restrainers while at the same time pressing the feet downwardly against the floor under the seat. This action contracts the upper or lumbar portions of the occupant""s psoas muscles and in so doing flattens his/her lumber spine effectively relieving chronic back pain.